Remote-controlled message display system with improved sign positioning means

ABSTRACT

A remote-control system is provided for enabling the automatic display of a particular selected message. The system includes a movable sign comprising an elongated curtain bearing a plurality of messages thereon and having an optically encoded array of apertures located between consecutive messages, with each such array being uniquely associated with one of the adjacent messages. The sign is bi-directionally driven by a pair of electric motors. A light source is positioned on one side of the curtain and a light-detecting system on the opposite side of the curtain so as to detect each code and develop a corresponding electrical signal. A comparator circuit develops a control signal indicative of correspondence or non-correspondence between the signal developed by a remote-control selector circuit and that developed by the light detecting system. The control signal causes the motors to move the sign until the selected message is displayed.

United States Patent McKee et al.

[ Apr. 9, 1974 REMOTE-CONTROLLED MESSAGE Primary ExaminerJohn W. Caldwell H DISPLAY SYSTEM H IMPROVED SIGN Assam/1iExamine/Ana ram M. Curtis POSITIONING MEANS Attorney, Agent, or FirmFitch, Even, Tabin &

. "1.. .2 L d k [75] Inventors: Chester W. McKee, Flossmoor; John D. McKee, Ottawa; C. Glenn Henderson, Aurora, all of ill. [57] ABSTRACT [73] Assigneez Teleweld, Inc Streator, m. A remote-control system is provided for enabling the automatic display of a particular selected message.

[ Filed! g- 1972 The system includes a movable sign comprising an elongated curtain bearing a plurality of messages [21] Appl' 279,529 thereon and having an optically encoded array of apertures located between consecutive messages, with 340/324 B, 18/282, 340/334 each such array being uniquely associated with one of [51] Int. Cl. G09f 11/22 the adjacent messages, The ign is bi-directionally Field of Search 340/ 373 driven by a pair of electric motors. A light source is 3 266 positioned on one side of the curtain and a lightdetecting system on the opposite side of the curtain so [56] References Cited as to detect each code and develop a corresponding UNITED STATES PATENTS electrical signal. A comparator circuit develops a con- 3,582,937 6/1971 Dozer et a1 340 324 B Signal indicative of Correslmndence 3,555,539 1/1971 "Richards 340/324 B Colrmspondence between the Signal developed by a 3,064,375 11/1962 Ely 340/324 B remote-control Selector circuit and that developed y 3,581,182 5/1971 Comstock et a1. 340/324 B the light detecting system. The control signal causes 3,351,830 11/1967 Samson et a] 318/432 the motors to move the sign until the selected message 3,588,656 6/1971 ShOfl'lBl' 318/282 is PATENFEMPR 9 m4 SHEET 2 [1F 2 REMOTE-CONTROLLED MESSAGE DISPLAY SYSTEM WITH IMPROVED SIGN POSITIONING MEANS I The present invention relates to message-display systems and, more particularly, to remote-controlled message-display systems for displaying one of a plurality of messages on a movable sign curtain.

One of the many applications of a remote-controlled message displaying system is that of remotely selecting the destination signs in one or more cars of a train, particularly a train of the rapid-transit type commonly employed for mass transportation in large cities. These signs typically comprise a plurality of destination readings or messages silk-screened onto an enlongated curtain made of Mylar or some other suitable material. The curtain is usually moved by two motor-driven rollers such that as the curtain unrolls from one roller it rolls up on the other. Thus, a desired destination sign is displayed by moving the sign curtain in some fashion until the desired reading is visible through a window, with a light source on the opposite or rear side of the curtain (in the case of a translucent sign) to increase visibility. Some such signs may be of the doublereading type in which the sign displayed on the outside of the train is also displayed on the inside.

One problem of sign curtains of this type stems from the fact that, as the curtain is moving, the two rollers must turn at continuously variable speeds because of the fact that the diameter of the curtain on each roller is continuously changing. In an attempt to maintain constant tension on the curtain, two motors have been used to drive the take-up and supply rolls independently. Nevertheless, in order to prevent either the slackening of the curtain or the tearing of the curtain caused by too little or too much difference between the torque of one motor and that of the other, the two motors should somehow be regulated such that they main tain a substantially constant amount of desired tension (i.e., within a predetermined tolerance range) on the curtain both when the curtain is moving and when it is stopped. Moreover, to assure that the selected sign is properly displayed, it is necessary to stop both motors in such a manner as to minimize coasting or overshoot and yet not damage the sign.

in some situations, it is desirable to control such signs remotely so that instead of having train personnel change the signs on each train, or even each separate car thereof, the signs may be changed by a central operator or even by an automatic train control. system. A problem often encountered in electronic systems of this nature occurs due to the relatively high transient switching voltages developed in electrically powered rapid-transit trains. Such transient voltages often exceed 600 volts and therefore tend to damage most conventional electronic control systems. Various other problems associated with such systems include false sign readings, end-of-curtain reversal, access time versus capacity, and means for verifying that the signs displayed on the various cars of the same train are all the same.

It is therefore an object of the invention to provide an improved remote-controlled message-display system. 7

It is another object of the invention to provide such a system which is economical to construct and simple to operate and is relatively immune to transient signal conditions.

it is a more specific object of the invention to provide such a system which has a large message capacity yet low access time and precision display.

Other objects and advantages of the invention are more particularly set forth in the following detailed de scription, and in the accompanying drawings, of which:

FIG. 1 is a block diagram of a remote-controlled message-display system constructed in accordance with the principles of the present invention;

FIG. 2 is an illustration of a moveable sign-curtain showing an array of coded indicia constructed in accordance with the principles of the invention; and,

FIG. 3 is an electrical schematic diagram of the system shown in FIG. 1.

With reference to FIG. 1, there is shown in blockdiagram form a remote-controlled message-display system for selectively displaying any one of a plurality of messages. In general, a remote message selector circuit is employed for enabling an operator (not shown) to select the message or destination sign to be displayed. It should be noted, however, that the principles of the invention apply equally as well to non-remotecontrolled message display systems. A code converter develops a command signal coded (e.g., in a binarycoded-decimal format) in accordance with the particular sign selected for display. Both the remote message selector 10 and the code converter 20 may be located in a central location (e.g., one of the cars or even a stationary train terminal) and the command signal thus generated may be applied to the remote unit (e.g., a rapid-transit train or each car thereof) by a suitable coupling device which may take the form of a cable network, a wireless transmission system, or any suitable equivalent.

The remote unit, which is typically located in one or more of the train cars near the destination sign display means, comprises moveable sign means in the form of a sign curtain which is rolled and unrolled on a pair of rollers 41 and 42 by a corresponding pair of drive motors M and M Sign curtain 40 bears a corresponding plurality of arrays 46 of predetermined coded indicia. Each array of coded indicia 46 is located between two consecutive messages and is uniquely associated with an adjacent message 45, as hereinafter described in greater detail with reference to FIG. 2.

The remote unit also comprises a photodetector system 50 which operates in connection with a light source to form a detecting meansresponsive to the coded indicia for sensing the particular message then being displayed and developing an electrical signal representative thereof. A code converter circuit converts the coded electrical signal developed by photodetector 50 to a signal suitable for application to a comparator circuit 70. The coding format employed may be binary, binary-coded-decimal, or any suitable equivalent, depending upon the particular application of the invention. Comparator compares the coded signal from the central unit with the coded signal from the re mote unit and develops a control signal indicating whether or not the two signals are the same. As long as the two coded signals are not the same, the control signal from comparator 70 causes motor control circuit to operate the motors in a given direction. When the two coded signals are equal, signifying that the message displayed corresponds to that selected by the operator, comparator 70 applies a control signal to motor control circuit 80 to stop the motors such that the message then displayed remains displayed until the operator selects a different message, as hereinafter described in greater detail.

With reference to FIG. 2, a portion of sign curtain 40 of FIG. 1 is shown in greater detail. In particular, two individual messages or signs (i.e., State Street and Michigan Avenue) of the plurality of messages 45 borne by sign curtain 40 are illustrated together with their respective arrays of coded indicia 46.

As an illustrative example of the coding technique employed in the embodiment of the invention depicted by the drawings, the State Street" sign has an array of seven binary coded decimal (BCD) apertures 46a-46g, with each aperture representing a logical one or high although the opposite logic format may be used wherein each aperture represents a logical zero or low. It should be noted that in FIG. 2 the solid-line apertures represent actual light-transmissive portions of sign curtain 40 (i.e., a logical one) whereas the dashed-line apertures represent opaque portions of sign curtain 40 (i.e., a logical zero) which, for other individual signs, are light-transmissive. It should also be noted that the apertures need not be actual openings in curtain 40 but rather they may be translucent or transparent portions of the curtain. The BCD coding format is achieved by having apertures 46a-46c represent the tens digit of the code number of the associated sign and 46d-46g represent the units digit thereof. Thus, as shown in FIG. 2, the State Street sign has a coded array representing the decimal number 77; Michigan Avenue, 78; etc.

In accordance with an optional feature of the invention, each coded array of apertures 46 further includes an additional read-enabling aperture 46r that, in cooperation with an additional light-detecting means (not shown in FIG. 2, see FIG. 3), enables the sensing of apertures 46a-46g by the detecting means only when the array of apertures 46 is in the correct position. Aperture 46r is located to one side of sign curtain 40 out of the path taken by signs 45 during movement of the curtain so that light transmitted through the sign curtain by signs 45 cannot pass through read-enabling aperture 46r. In effect, the light-detecting system for readenabling aperture 46r is in series with that of apertures 46a-46g and their power source so that the latter apertures are not energized until read-enabling aperture 46r is properly positioned. This prevents apertures 46a-46g from giving a false reading caused by the lighttran smitting portions of the signs 45 coincidentally matching the code of the selected sign.

In accordance with another optional feature of the invention, an indexing aperture 461' is provided with each array 46 to cause sign curtain 40 to stop with the selected one of signs 45 precisely aligned with the display window (not shown) through which signs 45 are displayed. As shown in FIG. 2, indexing aperture 461' is made substantially shorter than the other apertures and is centrally positioned relative apertures 46a46g, in the direction of travel of sign curtain 40, so that the coded apertures are illuminated prior to the indexing aperture. As described below in greater detail with reference to FIG. 3, the detecting means of the illustrated embodiment of the invention, in response to the detection of the coded aperture array corresponding to the selected sign (and after having been first enabled by means of read-enabling aperture 46r and its associated circuitry), causes the motors to slow down the travel of sign curtain 40 such that it momentarily stops and then gradually creeps forward until indexing aperture 461' is illuminated. By means of the circuitry associated with the indexing aperture, the motors are then absolutely stopped to thereby accurately align and dynamically brake the sign curtain. Thus, the system of the illustrated embodiment of the invention rapidly advances the sign curtain to the selected sign and then stops it precisely within the display window so that the selected sign is properly displayed within a minimum amount of access time.

With reference to FIG. 3, a more detailed electrical schematic diagram of the embodiment of the invention illustrated in FIG. 1 is shown. In particular, the code converter circuit 20 of FIG. 1 may be combined with the remote message selector circuit 10 and may be constructed in any conventional manner suitable for this application; hence, this portion of the circuit is not discussed in great detail. It may be desirable in some applications of the invention, however, to have code converter 20 comprise an integrated circuit read-only memory (ROM) which is initiallyprogrammed to provide an output signal only when a sign on curtain 40 is selected (i.e., no output signal is developed when a non-existant sign is selected). It should be noted that the remote signal coupling device 30 may also comprise any conventional means suitable for this application such as the cable network or wireless system discussed above.

Motors M, and M are energized by a bilateral switching means comprising a pair of relays R and R which are connected as shown in FIG. 3 such that they are mutually exclusive; that is, when relay R is actuated to energize motors M, and M so that they move sign curtain 40 in the forward direction, relay R cannot be actuated to energize motors M, and M, to move sign curtain 40 in the reverse direction. Suitable switching means, of course, maybe substituted for relays R and R without departing from the principles of this aspect of the invention. As illustrated in FIG. 3, both relays are de-energized.

In accordance with another optional aspect of the invention, a motor current regulation circuit 85 is provided to control the relative torque between motors M, and M to thereby maintain a substantially constant tension in the sign curtain. For this purpose, the torquecurrent characteristic of the motors should be known. Regulation circuit 85 comprises an amplifying transistor 81, a current-sensing resistor 82, and an emitterbiasing resistor 83. Relays R and R connect regulator circuit to motors M, and M such that the current of the motor driving the take-up roller (which, of course, depends upon which direction the sign curtain is moving) flows through current-sensing resistor 82 to develop a corresponding voltage at the base of transistor 81 which varies the collector current thereof. The collector of transistor 81 is connected in series with the motor driving the pay-out roller. Thus, when regulator circuit 85 senses an increase in torque in the take-up motor, it automatically increases the torque in the pay-out motor, and vice-versa, to maintain substantially constant tension in the sign curtain.

Photodetector circuit 50 comprises a plurality of light-sensing devices such as the light-sensitive resistors (LSRs) 5la-5lg shown in FIG. 3, the LSR's are positioned such that each one is respectively aligned with apertures 46a-46g of sign curtain 40. A plurality of switching transistors 52a52g are respectively coupled to LSRs Sla-Slg to develop a predetermined output (e.g., a logical one or high) whenever the corresponding LSR is illuminated. If desired, the lightsensing devices may be phototransistors which are electrically compatible with present-day integrated circuits. In addition, infrared light-emitting diodes (LEDs) may be used for the light source to provide immunity to shock and vibration as well as long life expectancy. The LEDs reduce the frequency of replacement and thereby minimize the need for faulty light source detecting means. Once again, the logic format may be reversed if desired.

ln accordance with an aforementioned optional aspect of the invention, a read-enabling LSR Slr is provided to activate the coded array of LSRs Sla-Slg, to prevent false reading due to the sign allowing light to fall on the LSR array, as discussed above. For this purpose, a switching transistor 52r is coupled to the output of LSR 51r to apply a suitable activating voltage V to LSRs 51a-51g when enabling LSR 5lr is illuminated.

An indexing'LSR 511' may be employed in accordance with another aspect of the invention to stop the sign curtain at the exact location for proper display, as also discussed above. For this purpose, a switching transistor 52i couples the output of LSR 51i to motor control relays R and R to stop motors M and M only when an index aperture is sensed (in addition to a matching code).

Comparator circuit 70 comprises a plurality of AND gates in the form of relay pairs 71a- 7lg which sense the correspondence or non-correspondence between the command signal from signal-selector 10 (via coupling device 30) and the coded indicia signal from photodetecting system 50 to develop a control signal which is applied to motor control circuit 80. It is understood, of course, that the relay pairs may comprise low-power reed relays or may even be replaced by suitable equivalents such as solid state logic components including AND gates, OR gates, NAND gates, NOR gates, and the like (some or all of which may be incorporated into a single integrated circuit (IC) or chip") without departing from the principles of the present invention. In accordance with this aspect of the invention, the relay pairs of comparator circuit 70 are connected in series; that is, the output of relay pair 71a is connected to the input of relay pair 71b, 71b to 71c, etc. lnthis manner, the most significant digit of the selected sign code is determined first; the next most significant digit, second; etc., so that the system displays the selected sign as rapidly as possible without wasting time backtracking.

At the output of comparator circuit 70 there are three terminals, A," B, and C." When the code number for the selected sign is the same as that detected by the photodetector system, a representative control signal is developed at terminal A. This signal renders conductive or turns on an inverter transistor 91 which renders non-conductive or turns off" an amplifier transistor 92. In accordance with this aspect of the invention, the output of amplifier transistor 92 is coupled to the input of an amplifier transistor 93 by means of a coupling capacitor 94 so that amplifier transistor 93 is initially turned on and then gradually'turned off again as capacitor 94 is charged. In this manner, a gradually increasing voltage is applied to motors M and M by means of driver transistors 95 and 96, which are connected in the configuration shown (often referred to as a Darlington Pair). Thus, the motors momentarily stop and then gradually move forward until the indexing circuit removes supply voltage V from the motor control relays which causes the motors to stop completely.

As long as the code of the selected sign is greater than that of the detected sign, comparator circuit 70 develops a forward control signal at terminal C which is coupled to forward motor control relay R by means of transistor 75. Transistor 77 couples a reverse control signal from terminal B to reverse motor control relay R when it is smaller.

In accordance with a further optional aspect of the invention, means for verifying that the destination signs in all of the cars of a given train may be established by providing a parity aperture 46p and LSR 51p coded to indicate whether a given coded array is odd or even; that is, the number of logical ones" for an array is odd or even. A parity comparator circuit compares the signal from LSR 51p with comparable signals from other locations (e.g.,.other cars of the same train-not shown) and applies an error signal to indicator whenever there is a discrepancy among the parity signals. Parity circuit 110 may further comprise means for enabling parity checking only when comparator 70 detects equivalence between the selected sign and the displayed sign. Such means may include an enabling signal from terminal A of comparator 70.

A suitable aperture 51m and LSR 51m may be provided to develop a signal whenever sign curtain 40 reaches the end of its travel. This signal is applied to an end-of-curtain detector which may develop a control signal that stops the motors, actuates an indicator, or the like, as desired for the particular application of the invention.

Thus, there has been shown and described an im proved message-display system that has a relatively large message capacity yet provides a relatively low access time (a system constructed in accordance with the illustrated embodiment of the invention has a capacity of 50 signs and an access time at 1.5 minutesy Th es ystem may be easily adapted to a wide variety of messagedisplay applications including, but not limited to, remote-controlled destination signs for rapid-transit train systems. Moreover, the system of the invention accurately aligns the messages with the display system to ensure proper message display. The system of the invention is relatively economical to construct and easy to operate, especially in connection with automatic train control systems that are presently becoming commercially popular.

lt will, of course, be understood that modifications of the present invention, in its various aspects, will be apparent to those skilled in the art, some being apparent only after study, and other being merely matters of routine design. As such, the scope of the invention should not be limited by the particular embodiment and specific construction herein described, but should be defined only by the appended claims, and equivalents thereof.

Various features of the invention are set forth in the following claims.

What is claimed is:

1. A message-display system for selectively displaying any one of a plurality of messages, comprising:

moveable sign means for bearing said plurality of messages and further bearing a corresponding plurality of arrays of predetermined coded indicia, each of said indicia arrays being located between two consecutive messages and uniquely associated with an adjacent one of said messages, said moveable sign means comprising a sign curtain adapted to be rolled and unrolled on a pair of motor-driven rollers;

means for visually displaying said messages individually;

means for moving said sign means relative to said visual displaying means to position a selected one of said messages for display, said sign moving means including bilateral switching means, a pair of drive motors connected to said bilateral switching means in a mutually exclusive manner so that said drive motors can be energized to move said sign curtain in one direction or the other but not both directions simultaneously, and a corresponding pair of rollers driven by said drive motors to wind and unwind said sign curtain on said rollers in a continuous manner;

detecting means responsive to said coded indicia for determining the particular message then in position for display and developing an electrical signal representative thereof;

message-selecting means for developing a command signal representative of the particular message to be displayed;

comparator means responsive to said coded indicia signal and said command signal for developing a control signal whenever said coded indicia signal corresponds to said command signal;

and brake means responsive to said control signal for stopping said moveable sign means with the particular message selected in position for display.

2. A message-display system in accordance with claim 1, which further comprises means for sensing the ends of said sign curtain in said visual display means to stop said rollers, said sensing means including a pair of end-of-curtain apertures respectively placed on the ends of said sign curtain.

3. A message-display system according to claim 1, which further comprises constant curtain tension control means, including a motor current regulating circuit comprising an amplifying transistor, a current-sensing resistor, and an emitter-biasing resistor for sensing the current of the motor driving one of said rollers and adjusting the current of the motor driving the other of said motors so that the torque of both motors is substantially the same.

4. A message-display system according to claim 1, in which said arrays of predetermined coded indicia comprise a plurality of light-transmissive apertures arranged in a coded sequence, and said detecting means comprises a light source positioned on one side of said sign curtain and a plurality of light-sensitive devices positioned on the other side of said sign curtain; said system further comprising means for minimizing access time for a selected message, including an elongated read-enabling light-transmissive aperture and an indexing light-transmissive aperture associated with each said message, and amplifier means including a coupling capacitor connected between said detecting means and said sign moving means, for causing said system to rapidly advance said sign curtain to the selected sign, substantially slow down the travel of said sign curtain when it approaches the selected message, and stop the travel of said sign curtain when said selected message is precisely arranged within said visual display means. 

1. A message-display system for selectively displaying any one of a plurality of messages, comprising: moveable sign means for bearing said plurality of messages and further bearing a corresponding plurality of arrays of predetermined coded indicia, each of said indicia arrays being located between two consecutive messages and uniquely associated with an adjacent one of said messages, said moveable sign means comprising a sign curtain adapted to be rolled and unrolled on a pair of motor-driven rollers; means for visually displaying said messages individually; means for moving said sign means relative to said visual displaying means to position a selected one of said messages for display, said sign moviNg means including bilateral switching means, a pair of drive motors connected to said bilateral switching means in a mutually exclusive manner so that said drive motors can be energized to move said sign curtain in one direction or the other but not both directions simultaneously, and a corresponding pair of rollers driven by said drive motors to wind and unwind said sign curtain on said rollers in a continuous manner; detecting means responsive to said coded indicia for determining the particular message then in position for display and developing an electrical signal representative thereof; message-selecting means for developing a command signal representative of the particular message to be displayed; comparator means responsive to said coded indicia signal and said command signal for developing a control signal whenever said coded indicia signal corresponds to said command signal; and brake means responsive to said control signal for stopping said moveable sign means with the particular message selected in position for display.
 2. A message-display system in accordance with claim 1, which further comprises means for sensing the ends of said sign curtain in said visual display means to stop said rollers, said sensing means including a pair of end-of-curtain apertures respectively placed on the ends of said sign curtain.
 3. A message-display system according to claim 1, which further comprises constant curtain tension control means, including a motor current regulating circuit comprising an amplifying transistor, a current-sensing resistor, and an emitter-biasing resistor for sensing the current of the motor driving one of said rollers and adjusting the current of the motor driving the other of said motors so that the torque of both motors is substantially the same.
 4. A message-display system according to claim 1, in which said arrays of predetermined coded indicia comprise a plurality of light-transmissive apertures arranged in a coded sequence, and said detecting means comprises a light source positioned on one side of said sign curtain and a plurality of light-sensitive devices positioned on the other side of said sign curtain; said system further comprising means for minimizing access time for a selected message, including an elongated read-enabling light-transmissive aperture and an indexing light-transmissive aperture associated with each said message, and amplifier means including a coupling capacitor connected between said detecting means and said sign moving means, for causing said system to rapidly advance said sign curtain to the selected sign, substantially slow down the travel of said sign curtain when it approaches the selected message, and stop the travel of said sign curtain when said selected message is precisely arranged within said visual display means. 